Field of the Invention
The present disclosure is directed to indexable cutting inserts and tool holders for parallelogram-shaped cutting inserts with positive cutting geometry. In one non-limiting embodiment, cutting inserts according to the present disclosure are particularly useful in peripheral rotary milling applications for machining difficult-to-machine materials. In another non-limiting embodiment, cutting inserts according to this disclosure are uniquely useful in peripheral rotary milling applications that generate segmented chips, for instance, when machining cast-iron and alloys, medium to high carbon steels, and fiber reinforced composite materials.
Description of Related Art
It is well known that cutting inserts suffer from a limited service life in peripheral rotary milling applications, especially when machining difficult-to-machine materials which include, for example, specialty metals such as titanium and titanium alloys, nickel and nickel alloys, superalloys, certain exotic metals, and fiber reinforced polymer composite. Cutting inserts comprising a positive cutting geometry on the axial cutting face and the radial cutting face are commonly employed in milling operations involving the use of a peripheral rotary tool holder with an indexable capability. The positive cutting geometry of the cutting inserts reduces the cutting forces resulting in a more efficient milling operation. A single-sided parallelogram-shaped cutting insert (often referred as A-Style insert) has a generally parallelogram-shaped profile when viewed from a point above the insert's top surface, with two long sides forming two main cutting edges and two short sides forming two minor cutting edges. These types of cutting inserts provide more efficient machining due to their positive cutting edges by providing the capability of a larger depth of cut due to the longer parallelogram cutting edges.
Using double-sided cutting inserts is getting popular simply because the doubled number of available cutting edges contributes to cost reduction benefits for both cutting tool end users and cutting tool manufacturers. However, the geometric design of a double-sided cutting insert for peripheral rotary milling is a more challenging task compared to a traditional single-sided cutting insert, because of the complexity of positioning a double-sided cutting insert in an insert pocket on a cutting tool holder in order to achieve sufficient positive cutting geometry all around the engaging cutting edge. A double-sided parallelogram-shaped cutting insert has a generally parallelogram-shaped profile when viewed from a point above the insert's top surface, with two long sides forming two main cutting edges and two short sides forming two minor cutting edges on each of the top and bottom faces. A double-sided parallelogram-shaped cutting insert comprises a negative cutting geometry at least on the radial cutting face.
Efforts in the industry to develop new or improved parallelogram-shaped cutting inserts have been directed toward achieving reduced cutting forces, reduced power consumption, increased cutting edge strength, and increased tool life. From the point view of geometrical design, maintaining a positive cutting action has been a fundamental goal of these efforts. However, conventional parallelogram-shaped cutting inserts for milling operation are only limited to either two positive cutting edges for a single-sided cutting insert or four generally negative cutting edges for a double-sided cutting insert.